Bobby pin



May 27, 1952 B. K. sNYDER 2,598,456

BOBBY PIN Filed Jan. 21, 1949 3 Sheetsrsheet 1 Uzzzt aad a? j Z 5 4 5 67 8 9 M 3 Sheets-Sheet 2 BOBBY PIN B. K. SNYDER May 27, 1952 Filed Jan.21, 19.49

-m -WFL B. K. SNYDER May 27, 1952,

BOBBY PIN Filed Jan. 21, 1949 3 Sl'xeetS-Sheeil 5 bazazaagfzzapazzaFIET.

Patented May 27, 1952 BOBBY PIN Burton K. Snyder, Chicago, ".Ill.,.assigner ltoGaylord Products, Incorporated, Chicago, Ill., `a

corporation of Delaware ApplicationJanu'ary 21, 1949,Serial No.7f1,787

l3 Claims.

'This invention relates to .hair fasteners "and is moreparticularlyconcerned with the provision of .a hair fastener of thebobby pin type comprising a piece of resilient wire bent intermediateits ends to 4form opposing hair clamping legs normally disposed incontacting engagement by means yof a connecting loop portion.

n The present invention contemplates the .provision `of a bobby pinconstruction in which the opposing legs are placed under'a relatively.high

initial tension or clamping force to. prevent accidental displacement ofthe 'bobby pin from a relatively small lock of hair or from a displaycard upon which the bobby pins are mounted for distribution and sale.yIn Athe manufacture of bobby pins, a piece of resilient Wire is bentinterme'diatev its ends to form opposing legs vand a connecting loopportion and it is well known in this art that such an operation Yplacesthe metal along the inner face of the loop -portion under compressionand places the metal on the outer face -o'f the Aloop portion undertension. To cause the legs of the bobby pin to exert a higher initialclamping force, the `present invention contemplates the provision of ashot peening operationen the outer surface of the loop Yportion Vtothereby cause the vmetal on -the outer surface to be placed undercompression. By shot peening the outer surface of the connecting loopportion of the bobbypin, it has been found'po'ssible to `open'the legsof the 'bobby pin to a greater width without exceeding the elasticlimits of the material. It will be 'appreciated that 'a bobby pin 'losesits usefulness lin clamping hair in position when the elastic limits ofthe material 'has 'been 'exceeded to cause the legs of the bobby pintobe set to an open spacedapart' position.

In Lthe preferred form of construction, the bobby pins are formed fromround, oval or halfround wire bent intermediate its ends to formopposing legsof gradually increasing width and decreasing thickness,with one of the legs'crimped transversely at spaced intervals andthroughout the major portion of its length. In this form ofconstruction, 'the bending'stren'gth of the legs at various pointsthroughout their length lis-proportional .to the leverage between the'various points and their connected ends, thus permitting a more uniformspread of ,the legs throughout their length without exceeding "theelasticflimits of *the various-sections. By -s'ho't peening 'the outer.surface of-theconnecting lo'op portion and the portions `.of `the Ylegs`adjacent thereto, the legs of the bobby pin may bewspreacl apart to agreater width than hasv heretofore been possible W-ithout exceeding theelastic limitof the material. This invention embodies other-novelfeatures, details yof construction and `arrangement Y-of' partswhich-are hereinafter -set'forth in the specification and claims andillustrated in the `accompanying drawings, wherein:

Fig. 1 is a topplan viewshowing a bobby pin embodying features ofy thisinvention.

Fig. 2 is a side elevational viewof same. Fig. 3 is a bottom plan viewof same.

Fig. 4 is a graph illustrating `the opening of unp'e'ened bobbypin's'ls'bje'cted to unit loads.

Fig.. 5 is a graph illus'tratin'githeopeningo pe'ened, heat-treated'bobby pins under unit load.

Fig. 6 is a graph illustrating the o'penin'g of peened, heat-treated;black japa'nned 'bobby pins underrunit load.

Fig. 7 is a graph-illustrating the'initia'l grip of unpeened bobby pins,peenecl 2bobby pins, and peened black 'japannedbobby pins.4

Referring now to theiirawings `for-a 4rdbetter understanding ofthis'invention, the bobby'pin is shown as preferably comprising falengthfof resilient wire 'bent intermediateitsven'clsfto form a loop.portion 6 and a pair-of depending legs 'l and S of gradually increasing`.width"an'c'ljiecreasing thickness" from the loop portion to their freeends. It is 'contemplated vthat the bobby pin may befformed from round,'oval or l.halfa round resilient steelwire. `The`-outerflegf11 ,isformed Athroughout the greater yportion `of its length with a pluralityof inwardly converging crimps having their Ybases 9 normally ldisposedin contact 'with the opposingleg. `A relatively large hair receivingfpocketll is formed at the inner end of th-e bobby pin `vand is -dened.,by the .leg 8, the uncri'mped portion l2 .oi the crimped leg l, andtheconnecting .loop ,portion 6.

W'hen a bobby .pin v'has beenformedin the manner illustrated anddescribed, the `metal deiini-ng the inner'suriace oi the lloop endo'ithe bobby .pin is under compression, while the metal deiining the outersurface .Id wof the loop -V end is urfde'r tension. To jincrease theinitial grip of the opposing legs "l and Y'8 and also to ,permit thelegs'tobe s'pra'dto' Va'wid'e open 4position without exceeding theelastic ^limit `oi the material., the outer' surace of vthe 'bobby pinvadiacent the loop .end f6 is shot peene'd to place vthe metal un'dercompression. The apparatus `for accomplishing the shoti-.peeningoperation may be of anysutabletypa'well yknown to thoseskilled in thelart, in which .relatively small steel shot are `directedagainst the outer `surface-oi the loop 'end ci the `lmilibyfpin atvarious' intensities which, for example, may be of from .002 arc heightto .012 arc height depending upon the carbon content of the steel Wireand the physical properties desired to be imparted to the bobby pin. Asillustrated in Fig. 5, groups of bobby pins were shot peened at variousintensities ranging from .002 arc height to .012 arc height in order todetermine which intensities were most desirable. In the chart it will benoted that bobby pins shot peened to an arc height intensity of .012offered greater resistance to initial load deflection than bobby pinsshot peened to an arc height of .002. However, the tests indicated thatthe deflection or spread of the bobby pin legs was substantially equalat the maximum unit load or the point at which the material reached theend of its elastic limit.

In making the tests of peened bobby pins and unpeened bobby pins it wasfound that 60% of the unpeened pins were sprung beyond their elasticlimits under the unit load E, While only 26% of the peened pins weresprung beyond their elastic limits under the unit load indicated atllE'H Fig. 7 in the drawings graphically illustrates the units ofinitial grip of unpeened bobby pins and shot peened bobby pins and itwill be noted that the initial grip of peened bobby pins greatly exceedsthe initial grip of unpeened bobby pins. It was further learned that theoverall stiiness and holding power of the shot peened bobby pinsexceeded that of the unpeened pins by 181/2%.

It is a common practice in this industry to japan pins afterheat-treatment to provide the pins with a relatively hard, smooth,moistureresistant surface. As graphically illustrated in Fig. 4, thejapanning operation appears to normalize or anneal the metal as japannedbobby pins have greater deflection under unit load than unjapanned bobbypins.

Fig. 6 in the drawings graphically illustrates the deflection under unitload of bobby pins which have been peened after heat-treatment and thenblack japanned after peening. It will be noted that these bobby pinswere subjected to a relatively greater unit load F and greater deectionl Without exceeding the elastic limit of the metal. A comparison of thetests between japanned pins and unjapanned pins is graphicallyillustrated in Figs. 6 and 5, respectively. In carrying out the tests ofbobby pins it was found that only 3.3% of the pins were sprung beyondtheir elastic limits under the unit load indicated at EL Whereas 60% ofthe unpeened, unjapanned pins opened at E and 26% of the peened,unjapanned pins opened at E.

In the manufacture of bobby pins of the type illustrated and described,the pins are rst formed on a conventional forming machine and thenheat-treated to enhance the physical Properties of the metal. The loopend of the bobby pin is then shot peened along its outer surface toplace the metal along the outer surface under compression. 'Iheheat-treated, shot peened pin is then japanned, if desired. The resultsof numerous tests indicate that heat-treated, shot peened pins may beopened to a greater degree than heattreated pins which have not beenshot peened, and that heat-treated, shot peened, japanned pins may beopened to a greater degree than heattreated, shot peened pins withoutexceeding the elastic limit of the metal. In subjecting the severaltypes of pins to a predetermined unit load,

it was found that the elastic limit of the metal was exceeded on 60% ofthe unpeened unjapanned pins, the elastic limit of the metal wasexceeded on 26% of the peened unjapanned pins, and the elastic limit ofthe metal was exceeded on only 3.3% of the peened japanned pins. Thetests further indicate that heat-treated, shot peened pins have a higherinitial grip than pins which are not shot peened.

In summarizing the advantages of the shot peening operation, shotpeening the loop ends of bobby pins definitely improves the initialtension, overall stiffness, and gripping qualities, and at the same timepermits the legs to be spread farther apart without exceeding theelastic limit of the metal. The tests indicate that shot peening thepins at increased arc height intensities further enhances the physicalproperties of the pins, that shot peened pins have an initial grip 25%greater than unpeened pins, and that the overall stiffness and holdingpower of shot peened pins exceeds that of the unpeened pins by 18%.

While this invention has been shown in but one form, it is obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without departing from the spirit andscope of the claimed invention.

I claim as my invention:

l. A bobby pin formed of resilient heat-treated metal, comprising a pairof opposing legs, and a loop connection normally urging said legs intocontacting engagement, the surface metal along the outer surface of saidloop connection and along the outer surface of adjacent portions of saidlegs being locally densied and relieved of residual tensile stresses.

2. A bobby pin formed of resilient heat-treated metal, comprising a pairof opposing legs, and a loop connection normally urging said legs intocontacting engagement, the surface metal along the outer surface of saidloop connection and along the outer surface of adjacent portions of saidlegs being locally densied and relieved of residual tensile stresses,said bobby pins being provided with a j apanned nish.

3. A Ibobby pin formed of resilient metal, comprising a pair of opposinglegs, and a loop connection normally urging said legs into contactingengagement, the surface of the metal along the outer portion of saidloop connection and along the outer surface of adjacent portions of saidlegs -being densied and relieved of tensile stresses occasioned byforming the loop, said bobby pins being provided with a japanned nish.

BURTON K. SNYDER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS 15,939 Great Britain of 1893

